Lithium-based battery and capacitor cells are used in many articles of manufacture. Some of the larger embodiments of these cells are used as electrical power sources in automotive vehicles and in other relatively large power-requiring consumer products. Electrodes for many lithium-ion based electrochemical cells are often formed by depositing porous layers of resin-bonded particles of active electrode material onto the opposing major surfaces of a suitable metallic current collector foil. Although portions of the foil may be curved or folded in the assembly of an electrode in a cell, the surfaces of the current collector foil, to which the electrode material is applied, are generally flat and smooth. Cells using such electrodes are often formed by stacking or rolling like-shaped, alternating, thin porous anode and cathode material layers, held apart by coextensive, thin, porous, electrically resistant polymeric separator layers, and by infiltrating the facing porous cell materials with an electrolyte solution formed of a suitable lithium salt electrolyte dissolved in a non-aqueous lithium ion conducting solvent.
During discharge of a lithium-ion battery, lithium ions are de-intercalated from a lithium-containing anode material into the surrounding electrolyte with the concurrent release of electrons into the anode current collector and then into an external DC circuit, which includes a power consuming device. Within the cell, lithium ions are transported through the electrolyte solution, through the pores of the separator, and are intercalated into particles of a lithium compound of the cathode material (also carried on a metallic current collector) as electrons enter the cathode material from the external circuit. During discharge of a lithium capacitor, the discharge of electrons occurs as adsorbed lithium ions are released from the anode material and adsorbed anions are released from the cathode material. The total energy and effectiveness of such lithium cells depends largely on the capacity of the respective electrode materials, bonded to their current collector, to interact with the electrolyte solution and to receive and release lithium ions. The energy and effectiveness of such lithium cells also depends on ability of electrons to flow from the particulate electrode materials to and from their metal current collector foil.
Anodes for lithium cells are often prepared by forming a porous resin-bonded layer of graphite particles (which can hold lithium atoms) or particles of a lithium compound, such as lithium titanate, on both major surfaces of its current collector foil. The anode current collector foil is often a copper foil. The copper foil is often formed of electrodeposited copper having a thickness in the range of about five to fifteen micrometers. The thicknesses of the adherent porous layers of particulate anode material, which are suitably bonded to the opposite surfaces of the copper foil current collector, are typically up to about 100 to 150 micrometers. The energy-producing capacity of the lithium cell is dependent on the composition, nature, thickness, and area (amount) of the coating of anode material on the flat surfaces of its copper current collector. There remains a need for improvement in the structure of the surfaces of the copper current collector and of the bonding of the porous layer(s) of particulate anode material applied to its surfaces.